Have you tried toktumi? It's $14.95 per month and offers unlimited u.s/Canada calling via phone, 3g and voip.
Their iphone/bb apps rock and they will soon be offering unlimited texting later this summer. Oh and they have Canadian numbers.
This is another <possible> solution.
http://www.toktumi.com/
http://itunes.apple.com/ca/app/line2...319185557?mt=8
PS:via RFD